Telephone "calling" cards are well-known in the prior art. Such cards typically include a memory comprising a magnetic tape or other storage media affixed to the card. Data in this storage media typically identifies the card number and the account to which the card has been assigned, and it may also comprise an authorized user's personal identification number or "PIN." To effect a toll call, the card is inserted into a cardreader (or the bearer is prompted to enter the card data via the telephone keypad) and relevant information is read from the card for subsequent billing.
Some cards include a data processing capability in the form of a microprocessor and an associated control program. Such "smart" cards have been used in prior art voice command systems wherein it is important to limit access to certain services to only authorized users. For example, U.S. Pat. No. 4,827,518 to Feustel et al describes a speaker verification and voice command system wherein speech templates are stored in the card. To verify the user's identity, a comparison is made between a plurality of reference speech templates stored in the card and a test template formed from a word or words spoken by the user at a transaction terminal. A similar system is described in U.S Pat. No. 3,896,266 to Waterbury.
Such prior art systems are effective but are significantly complex and somewhat expensive. They require the use of specialized hardware to generate and store the coded information on the cards, as well as the use of precise verification algorithms to discriminate the voice of an authorized user from all unauthorized users. Moreover, prior art voice verification schemes do not always work effectively over the telephone network. Generally, this is because the telephone network is a challenging environment that degrades the quality of speech through the introduction of various types of noise and band-limitations. Such economic and technological limitations have in large part prevented voice command calling systems from being commercialized.
There is thus a need for methods and systems that overcome these and other problems associated with the prior art.